Problem: An object is launched from a platform. Its height (in meters), $x$ seconds after the launch, is modeled by $h(x)=-5(x+1)(x-9)$ How many seconds after launch will the object hit the ground?
Explanation: The object hits the ground when $h(x)=0$. $\begin{aligned} h(x)&=0 \\\\ -5(x+1)(x-9)&=0 \\\\ \swarrow &\searrow \\\\ x+1=0\text{ or }&x-9=0 \\\\ x=-1\text{ or }&x=9 \end{aligned}$ We found that $h(x)=0$ for $x=-1$ or $x=9$. Since $x=-1$ doesn't make sense in our context, the only reasonable answer is $x=9$. In conclusion, the object will hit the ground after $9$ seconds.